And Obama is weighing broadening a map that already appears big and red into four more states. A top adviser, former Senate Majority Leader Tom Daschle, said Obama is considering expanding his active campaign back into North Dakota and Georgia, from which he’d shifted resources, and into the Appalachian heartland of West Virginia and Kentucky.

“Those states are much more in play than they were a week ago,” Daschle said.

The biggest concern for Republicans in this would be Georgia and Kentucky, where two incumbent Republican senators are now in the middle of unexpectedly competitive races. If Obama puts serious money and time into the state (personnel, ads, and visits), the two Democratic challengers could potentially ride his coattails and take out Mitch McConnell and Saxby Chambliss.

Democrats would love to win both races not only because it helps them build to a 60-seat majority, but because they could symbolically avenge previous losses: Max Cleland, who was defeated by Chambliss in a nasty campaign, and Daschle, who Republicans successfully targeted for defeat in 2004 because of his role in leading opposition to the Bush agenda as Senate Minority Leader (a position now held by McConnell).